Balancing mechanism for aircraft



April 29, 1924.

J. P. TARBOX BALANCING MECHANISM FOR AIRCRAFT Original Filed Feb. '7,1913 2 Sheets-Sheet 1 April 29 1924.

J. P. TARBOX BALANCING MECHANISM FOR AIRCRAFT Original Filed Feb. 7,1913 2 Sheeis-$heet to the direct operative interconnection of- Patentepr. 2, 1024.

JOHN P. TARBOX, OF GARDEN CITY, NEW YORK, ASSIGNOR TO TARBOX SAFETY AIR-CRAFT 00., OF WASHINGTON, DISTRICT OF COLUMBIA, A CORPORATION OF DELA-.WARE.

BALANCING MECHANISM FOR AIRCRAFT.

original application filed February 7, 1913, Serial No. 746,919. Dividedand this application filed January 11, 1921. Serial No. 436,410.

To aZZ whom it may concern:

Be it known that T, JOHN P. TARBOX, a citizen of the United States,residing at Garden City, in the county of Nassau and State of New York,have invented certain new and useful Improvements in BalancingMechanisms for Aircraft, of which the following is a specification.

' My invention has to do with those relative adjustments and controlmovements of the stabilizing and control surfaces of an aircraft whichensure effective lateral and longitudinal equilibrium and adherence tocourse. The particular mechanisms claimed herein are divided out of myco-pending application S. N. 746,919 filed Feb. 7th, 1913, interlockingbalancing system. Through these mechanisms several of the fundamentalprinciples of the parent application are applied the various stabilizingand control surfaces, i. e. one freed from intermediate servo-motorpower devices and therefore decidedly more simple. In the accomplishmentof this the power for the purposes of automatic relative adjustments isobtained in the one case from one of thehorizontal stabilizing surfacesof the machine and in the other from a set of auxiliary motor surfacesespecially provided or constituted.

Of the drawings,-Fig. 1 is a diagrammatic illustration arranged inperspective of one such embodiment, and

Fig. 2 is a similar illustration of another embodiment.

The numerals applied are those used in the parent application.

The balancin devices shown in Figure 1 are of the type s own in my U. S.Patent No. 1,239,636 granted Sept. 11th, 1917. They comprise liftingvanes 200 mounted substantially in the horizontal plane, or at anyslight angle thereto laterally which may be desirable from thestandpoint of advantages obtained through the use of dihedral angle orother well known principles. They are fixed to freely rotate aboutvertically extending axes 201 mounted in antifriction bearings at theopposite lateral extremities of the craft. They are oblique in thedirection of their length to the longitudinal axis of the craft, theirlengths converging to a point in advance of the transverse lineconnecting them. Their outermost ends measured from the axes 201 arelonger than the innermost ends, whereby the head resistance or windpressure on the outermost ends is greater than that on the innermostends, and whereby the controlling torque brought about by the windpressure is in opposite directions on the opposite vanes. This may bebrought about in any other suitable manner as for instance by theaddition of surfaces 204 fixed to the axes on the outboard side in eachcase.

These vanes are connected together for retention in their normal angularrelation as respects each other, and for movement about their axes inunison, by cords 202 connecting longitudinal crossbars 203 secured tothe rotatable axes 201.

For a detailed description of the action of these vanes underunbalancing conditions, reference may be made to my patent abovereferred to. For the purpose herein sufiice it to say that when it isdesired to bank the craft, movement of the vanes 200 is brought about ina clockwise or anticlockwise direc tion depending upon the direction ofthe turn it is desired to make through the operation of the verticalrudder 82 of the craft.

movement of the vanes 200 to bank the craft was brought about through avariation of the connections between thevanes. In Figure 1 it is broughtabout bychanging the relative angle of obliquity of the auxiliaryoutboard surfaces 204. For this purpose the surfaces 204 are mounted onhorizontally extending axes 203 revolvable in bearings fixed to androtating with the axes 201, whereby while the axes 203 are revolvable,they are nevertheless fixed radially with respect to the axes 201 andvanes 200. The normal angle of obliquity of the surfaces 204 ispreferably 30 or 10 and in. the same direction forwardly whereby thereis exerted a lifting effect upon them. Through cord connections 205 withpulleys 206 on shaft 203*, the connection being made by way of blocks207 closely adjacent to the axes 201, the surfaces 204- may be freelymoved simultaneously in opposite directions, withplace. This is broughtabout through the increase of pressure on the long end of that vane 200which is rotated to a position close to thetransverse axis of the craft,as will be well understood, the vane 200 in this position having agreater head resistance and secondly having a greater torque exertedupon it on the outboard side. This will be readily understood from Whathas pre vi ously been said about the vanes 60 of Fig- The pressureresponsive device 108 operates the horizontal rudder 121 automaticallythrough cords 208. These cords connect with rudder 121 throughdifferential 209-210 and cords 211. A manual operating lever 213 alsoconnects with the horizontal rudder through differential 209210,connection being made by cords 212. Cords 212 connect with arm 214 ofthe throttle lever 216. Connected with the opposite end of arm 214 iscord 217 secured to foot lever 218 whereby the throttle may be manuallycontrolled. Intermediate lever 215 connects at one point with lever 214at its middle directly with throttle lever 216 and at the other end withstandard of position 219 connected with fixed part 220, whereby thethrottle is operated to vary the supply of power in accordance with theposition of the craft.

Vertical rudder 82 is operated through cords 221 to which are connectedcords 205 for operating the controlling surfaces 204 of the vanes 200whereby when the vertical rudder 82 is moved to make a turn, thesurfaces 204 are operated in the proper direction torotate the vanes 200to properly bank the chaft. Manual operation of the vertical rudder 82is effected through differential 222-223 connecting by cords 224 withmanual operating lever 225. The locking device 96-9798-99 is connectedwith cords 202 of the balancing devices 200. The interlocking member 227is connected directly in cords 221. One of the abutments 96 and 97 isrotated into the path of movement of the abutments on member 227whenever the balance of the craft-is not such as to warrant a turn inthe direction desired. The lost motion connection 50-51 of Figure 1 ofmy Patent No. 1,367,839, of which this is a division, has not been shownbut it is understood that it will be included in the connection of thecords 202 with pulley.99. The operation of this device has been fullyexplained in connection with Figure 1 of the parent application.

Connected with differential 222223 is an operating cord 228 throughwhich vertical rudder 82 may also be operated. This cord is operatedfrom a pulley on rotatable shaft 229 having at its lower end a hub 231having a sliding connection with the trunk of a T-shaped member 230, thetransverse part of which is slotted. Within this slot slides a block 233having sliding connection between abutments 234235 with cord 208connected with pressure responsive device 108.

Springs 232 at opposite ends of member 230 retain it and the shaft 229in a central normal position. A fork on the lower end of lever 236pivoted to fixed point 237, strad dles a block 233. The upper end oflever 236 passes through a block 238 pivotally connectedwith lever 225and constitutes a lost motion device. The distance of the fixed point237 from the block 238 may be made as small or as great as desired, thusintroducing a greater or less degree of lost motion between the lever225 and the lever 236.

As long as the craft is moving straight ahead, the variations ofpressure on the device 108'cause it to operate cords 208 andautomatically govern the longitudinal balance of the craft throughconnections with the horizontal rudder 121. During this time the member230 is moved back and forth against the pressure of the springs 232(which is far less than the controlling force of device 108) withoutaffecting the normal position of the shaft 229. amount of lost motionbetween block 233 and abutments 234 235 is such that unless pressureconditions are abnormal, abutments 234 and 235 do not engage the block233. When, however, lever 225 is moved to make a turn, the block 233 ismoved to one end or the other of the slot in member 230, this by thefirst operation of movement ofthe lever 225. Thereafter as is wellunderstood, the block 238 simply slides upon the upper end of the lever236 without producing any appreciable movement thereof. Thus block 233is placed in one end or the other of the slot in member 230 inaccordance with the direction of the turn contemplated. Thereaftershould the speed of the craft fall, or should the Wind pressure ondevice 108 be reduced for any reason whatsoever, the en-- gagement ofabutment 235 with block 233 under these conditions, will rotate shaft229 and through its operation of vertical rudder 82. reduce the angle ofturn to the safe value under existing conditions. Under conditions ofextremely reduced pressure in which no turn at all would be warranted,the extreme movement of device 108 might entirely nullify the action ofrudder 82.

Also the neeaooc The degree of effect of the. device 108 upon the rudder82 may of course be made anything desired by the simplest imaginableproportioning of the intermediate connections.

The value of this differential interlock between the pressure responsivedevice 108, the manual control lever 225 and the vertical rudder 82 liesnot only in the fact that dangerous turns under adverse conditions ofspeed and pressure are prevented as in the case of the system of myparent application, but also and perhaps more greatly in the fact thatthe angle of turn once commenced, will be reduced should conditionsafter the turn is commenced make its continuance at the same angledangerous. It is a well known fact that several fatal accidents haveoccurred through the making of a sharp turn at substantially rightangles to the direction of the wind. This has usually hap pened when thecraft was going against the wind and its actual speed was comparativelylow. Upon turning at substantially right angles to the direction of thewind at this low velocity, the sustaining force has been inadequate tomaintain the craft under control or to sustain it in the air at all.With the system of my invention as shown in Figure 1, immediately thatthe pressure on device 108 begins to fall, as it assuredly will as soonas the turn is commenced under the described conditions, the angle ofthe turn is decreased proportionately, and'although the aviator maymaintain manual control through lever 225 in its extreme position, thecraft is positively prevented from taking a turn sharper than iswarranted at any instant by the then existing conditions. A study of theoperation of this interlock will show that its effect is not sudden andir regular, but is easy and uniform as are thevariations in pressure onthe device 108. The aviator is thus not disturbed through the automaticaction of this interlock.

I have herein shown also the positive stop interlocks 102 and 132 of theparent case, associated respectively with rudders 82 and 121. The device102 may be entirely omitted if desired when the device 230 isincorporated. The device 230 is not subject to the objection that anaviator may find with the device 102 in that the device 102 is apositive stop and is liable to disturb manual operation to a slightextent until one becomes used to it.

The pressure responsive device 108 which is the front stabilizingsurface of the aeroplane is of form shown in Figure 3 of the parentapplication, is biased against wind pressure through springs 240 on rods239 pivotally connected at one end to the device 108 and passing1through apertures in the Outriggers or ot er fixed art of the craft. Theupper ends of the ro s 239 are headed over or provided with nuts toconfine springs 241 on the rod between heads 239 and forks 242 on atransverse shaft 243 mountel in suitable bearings. This shaft isrotatable through the ear and worm 24A and 245 from longitudinallyextending shaft 246 provided with manually operable hand wheel 247. Byaltering the position of the forks 242, the pressure of springs 241 isaltered and the resultant pressure of springs 240 is therefore alteredwithout in any way affect ing the freedom of movement of device 108.Thus the normal balancing angle of the craft may be freely altered bythe aviator from his seat without in any wise interfering with thebalancing functions of device 108.

The cut-out for the pressure responsive device 108 in the form of lever249 connected with cord 208, is provided as in the case of the system ofFigures 1 and 1 Referring now to Figure 2, similar devices and similarparts have been similarly numbered. The embodiment of Figure 2 differsfrom that of Figure 1 principally in the character of the interlocksbetween the pressure responsive device 108, and the horizontal andvertical rudders 121 and 82. Instead of providing positive stopinterlocks of the type of Figures 1 and 1 of the parent case" (theinterlocks 102-132), these interlocks are entirely omitted andinterlocks functioning as does the device 230 of Figure 1 aresubstituted. The form of these interlocks, however, is decidedlydifferent from that of Figure 1. In the system of Figure 2 they consistrespectively of links 252253, pivoted link 253 at its middle and link252 at one end as shown by larger dotted line circle to ,fixed parts 254and 255. These links are respectively oscillatable about their pivots byconnection with the cords 208 between the pressure responsive device 108and the. horizontal rudder 121. Obviously the positions of the links areindicative of the speed and pressure conditions as measured by thedevice 108.

Connected with link 252 by means of any suitable slide in the slotthereof is lever 256 having connections at an intermediate point withmanual operating cords 212 for the horizontal rudder 121, and havingconnection at its opposite end with cords 260 connected with manualoperating lever 213. As shown in the normal position of the lever 256,its connection with the slot in link 252 lies directly over the pivotalpoint of link 252 with the fixed part 254. By means of the linkconnection 257257 of this end of the lever 256 to arm 258 on controllever 213, the lever 256 is shifted longitudinally of the link 252 tocarry its point of connection thereto away from the pivot toward one endof the slot whenever the control lever 213 is moved. For the purposes ofclarity, the link 252, the lever 256 and the link position.

257 have been shown at an angle to each other. This is the relativeposition they would occupy under abnormal conditions of pressure andspeed of device 108 when the control lever 213 was moved. But undernormal conditions of flight, it is to be understood that the link 252and the lever 256 are-substantially parallel, and likewise atsubstantially right angles to the connections 208, 212 and 260. Theseconnections are laterally freely'flexible and of such length as topermit such lateral movement without substantial lost motion in thecables.

'Under these normal conditions'whenever control lever 213 is moved, thelever 256 is moved longitudinally and its pivotal connection with link252 shifted toward one end of the slot. The link 252 being substantiallyparallel with it, howeven'it exerts no appreciable effect upon itsangular Through connection 260, however, the angular position of lever256 is altered to move the horizontal rudder 121 to the desiredposition, and under such conditions, the movement of the rudder 121 isapproximately proportional to the movement of the control lever 213.When the pressure and speed conditions are abnormal, however, theangularity of the link 252 15 changed with respect to link. 256. As longas the control lever 213 is in normal position, however, and the craftis proceeding in a straight line, this is without effect, for

the point of connection of lever 256 to link 252 lies on the pivot oflink 252 to fixed part 254. When ascent or descent is attempted underthese conditions, however, the point of connection of lever 256 isshifted toward the end of the slot in 252 as described with the resultthat the intended movement of rudder 121 is either augmented ordecreased in accordance with the existing conditions. Thus to take aspecific case, when the speed is high, the pressure on device 108operates a cord 208 in the direction of the arrow and carries link 252counterclockwise as shown. Then when control lever 213 is movedclockwise to deflect rudder 121 upwardly through connections 212, 209,210 and 211, the movement of cord 212' and hence of rudder 121 isaugmented through the clockwise movement of the upper end of lever 256.Thus an increased angle of ascent is permissible as is warranted by theexisting high pressure conditions. Under low pressure and speedconditions, clockwise movement oflink 252 would take place, with theresult that the upper end of lever 256 would be moved counterclockwisein a direction opposite clockwise movement of lower end, and themovement of rudder 121 to turn the craft upwardly is decreased, andunder extreme conditions may be nullified altogether, the lereeaooe ver256 under such extreme conditions moving as it were about its pointlofconnection to cord 212 as a pivot. The same functioning takes place whenthe lever 213 is moved counterclockwise to turn the craft down wardly,the point of connection oflever 256 beingmoved to the lower end of theslot in link 252 as before but with opposite efi'ects.

Thus it is apparent that this diflerentia'l interlock automatically andinstantaneously at all times adjusts the resultant movement of thehorizontal rudder to suit the pressure and speed conditions under whichthe craft is traveling. By suitable proportionment of parts thisadjustment may be made such as to remove the control of the craft as faras may be desired from the danger points under adverse conditions. It isthus impossible for an aviator to take such an angle of ascent as tostall his craft or to take such an angle of descent as to plunge itbeyond control. Moreover should the control lever 213 be moved tooperate the rudder 121 at any instant when, pressure conditions do notjustify its operation, and that operation is reduced or annulled throughthe interlock 252256, if the control lever is momentarily held in itsposition, the desired movement of the rudder takes place automaticallyat the instant pressure and speed conditions warrant it, for ensuingmovement of the link 252 operates lever 256 to impart the requisitemotion to operatingcords 212. This is of extreme value when operating invariable or gusty winds, the effect of which can be gauged by an aviatoronly with extreme difficulty.

Associated with the link 253 is the control mechanism for the verticalrudder 82. A lever 261, the lower end of which is pivoted slidably .andnormally centrally of the slot in link 253, is connected atv its middle.

to operating cord 221 which connects the vertical rudder 82 withdifferential 274-27 5. The upper end of this lever is connected by cords265 with bell crank 264 associated with control lever 225. Lever 261like the lever 256 is normally substantially parallel to link 253 andsubstantially at right angles to cords 208 and 221. Its lower end isconnected by link 262 with the arm 263 of the pivoted or swiveled tolever 225, pin 268 passing through the block and connected with pulley269 journaled independently of lever 225 on fixed part 270, andconnected b cord 271 with one arm of differential 272-273 connectingwith operating cords independently naeaoee 205 which extend to theoutboard rear extremities of the vanes 200. These extremities of thevanes 200 are made flexible so that they may be warpedup or downsimultaneously in opposite directions to alter the head resistance andhence the relative torques of the-vanes 200 about their axes. Theopposite end of the lever 272 of differential 272-273 is connected tocontrol cable 221 leading to the vertical rudder 282 as aforesaid.

The interconnecting cables 202 between the vanes 200 are also connectedto operate the vertical rudder 282 by means of cables 277 connectingwith the arm 274 of differ ential 274-275.

The interlock between the vertical rudder 82 and the lateral balancingvanes 200 is provided in this case between the cables 202 and the cable265 connected with the bell crank 264. A lost motion device of the blockand pin type is clearly shown in this connection and it is numbered50-51. The rotated abutments 9697 co-operate with abutments 227 carriedb the cord 265.

The operation is as ollows: As long as pressure and speed conditions aresuch as to warrant turns of any desired degree, right or left,substantially the entire movement of control lever 225 is imparted tovertical rudder 82. At any instant, however,

' if the pressure and speed conditions are not such a will warrant thedesired turn, the shifting of the lever 261 longitudinally of the slotin link 253 which occurs for each movement of-lever 225, decreases to agreater or less degree the resulting movement of the vertical rudder 82and hence the degree of the resulting turn. Should the craft betraveling at too slow a speed in a straight line to warrant an abruptturn, such turn cannot be made either to right or to left, and underextreme imaginable conditions, it may be impossible to make such a turnat all. If, however, the operator desires to take the risk, he can cutout the pressure responsive device 108 by locking t e same by the use oflever 249. But unless he deliberately chooses to take chances, he isautomatically guarded against danger.

Also in making a sharp turn at substantially right angles to the wind,the progressive falling ofi of the sustaining force as the turn is madeeflects proportional movement-of link 253, with the result that theangle of turn is decreased until the craft gains headway, whereupon andsimultaneously the rudder is returned to the point necessary to completethe turn. The operator has only to move the control lever 225 to theposition he desires and hold it there, and the craft will take the turndesired at the maximum safe rate.

initial movement of the. control lever 225 effects through lost motiondevice 267268 flexing of the outer ends of vanes 200, with the resultthat the craft is given an initial angle of bank. A tracing of theconnections will show that the efi'ect of flexing the vanes 200 is thesame as changing the angle of obliquity of the auxiliary surfaces 204 ofFigure 1. Subsequent to this, the angle of bank is increased inproportion to the increase in the degree of the turn by means of theconnection of cable 221 with differential 272-273. The combined actionof gravity and the equalization of the pressures on the vanes 200 afterthe bank is entered upon, acts to limit the angle of bank to a definitevalue for each angle of turn as described in m Patent No. 1,239,636above referred to. Adjustable masses and surfaces connected with theaxes 201 are not shown but they may be used if desired as shown inFigures 1 and 2 of the parent case herein and also in the patentreferred to.

If the craft happens to be unbalanced in a direction opposite to that inwhich it is desired to make a turn, the interlock 9'697- 227 preventsmovement of cable 265 to operate vertical rudder 82 until the balanceisrestored to a predetermined point, which may be at normal, or on oneside or the other of normal as choice may decide. Under such conditions,the yielding connection 266 between lever 225 and bell crank 264prevents springing or breaking of parts upon sudden and impropermovements of control lever 225 under these conditions. In fact lever 225may be moved against the tension of spring 266 to institute the turn,and as soon as the balance is restored to a oint warranting the turn,cable 265 and ell crank 264 are released, and under the tension ofspring 266 are moved automatically to "operate therudder 82 to thedesired point. The initial movement of control lever 225 under theseconditions preliminarily operates cable 271 to flex the vanes 200 tobring about the initial angle of bank. This action facilitates therestoration of balance, through the resulting increase in correctiveforces exerted by the vane 200 on the lower side and correspondingdecrease of lifting foiceof vane 200 on the high side. These operationsare substantially as in the system of Figures 1 and 1 of the parentcase.

If desired, the form of the differential interlock between pressureresponsive device 108 and horizontal rudder 121 may be made the same asthat between device 108 and vertical rudder 82. In such case, the link252 will be centrally pivoted instead of ivoted at one end, andconnection made wit lever 213 by means of connection of link 257 with asuitable bell crank connected with the lever. In such case, however, thedifierential action of the lin 25 2 be the -1 whether rudder 121 isturned up or down, just as in case of vertical rudder 82, the effect isthe same Whether rudder 82 is turned to right or to left. In other Wordsif the effect of device 108 augments the movement of the rudder in onedirection at any instant, it will at the same instant should movement ofthe rudder be in the opposite direction similarly augment that movement.The construction illustrated, however, is preferred.

Through the connection 277 ,to the vertical rudder 82, the rudder servesas a tail vane, steadyingthe action of the balancing vanes 200.

A plurality of balancing vanes 200 may be connected in multiple totransverse cables 202 as indicated clearly by the additional axes 201beyond the axes 201. The vanes 200 on these additional axes 201 may bemounted in the same plane or in difierent planes from the vanes 200, butthe essential feature is that their movement about the axes takes placein unison. The advantage of the multiple number of balancing vanes 200as distinguished from a single very large vane on each side of the craftis that the moment of inertia is much smaller, whereby the action isfaster. Of course the outer ends of these additional vanes 200 may bearranged to be flexed as are the ends of these vanes 200 illustrated. Orelse additional surfaces 204 may be used in connection with the axes 201Obviously these mechanisms may be used for the relative adjustment ofother forms of surfaces than those described, and the mechanismsthemselves may be varied in form without departing from the real spiritof applicant's invention. Applicant would have it understood that theappended claims are intended to cover all embodiments of his inventionnot departing from its generic spirit.

What I claim is:

1. In an aircraft, a rudder, anemometric means connected to directlyeflect actuation of said rudder, manually operable control means alsoconnected to efi'ect actuation of the rudder, and an anemometricallycontrolled means to regulate the extent of move-- craft andindependently of the manual control.

3. In combination an anemometer device, a rudder, operating meanstherefor, a direct operating connection between the anemometer deviceand the rudder effective to operate the rudder independently of thefirst named meaooe operating means, and means for at will locking outthe anemometer operating connection.

4. In an aircraft automatic lateral balancing means, embodying mechanism"to modify the normal operation thereof, directional steering means forthe craft and control means therefor connected together todifferentially actuate said modifying mechanism.

5. In an aircraft automatic lateral balancing means, embodying mechanismto modify the normal operation thereof, directional steering means forthe craft and control means therefor connected together todifferentially actuate said modifying mechanism, and embodying avariable ratio connection to said control means.

6. In an aircraft a propelling motor, control means therefor, and astandard of position with respect to the earth governing said controlmeans.

7. In an aircraft, an adjustable horizontal 1y disposed stabilizingsurface, an elevating rudder connected therewith and lying in the rearthereof, means for adjusting the stabilizing surface from the seat ofthe operator, which adjusting means by reason of said interconnectionalso moves said elevating rudder in the adjusting movement, andindependently operable means for actuating the elevating rudder.

8. In an aircraft, an elevating rudder, and a horizontally disposedstabilizing surface connected to directly operate said elevating rudderand normally yieldingly held in a determinate angular relation to theair rush independently of said elevating rudder.

9. In an aircraft a horizontal stabilizing surface normally yieldinglyheld in a determinate' angular relation to the air-rush, an elevatingrudder operated directly thereby, and means for locking'said stabilizingsurface in adjusted positions.

10. In an aircraft an adjustable horizontally disposed stabilizingsurface, a flexible adjusting connection extending from the stabilizerto a point adjacent the operators seat, a self locking manipulatingmember at that end of the connection, an elevating rudder and operatingmeans therefor independent shaft connected with said stabilizing surfaceeeaooe and also extending transversely of said frame, a worm gearcarried by said shaft, means for operating the Worm gear from theoperators seat, an elevating rudder and operating means thereforindependent of said stabilizer adjusting means.

' 13. In an aircraft a longitudinally projecting frame, a horizontalstabilizing sur; face adjustable about an axis extending transversely ofsaid frame, an adjusting shaft connected with said stabilizing surfaceand also extending transversely of said frame, a Worm gear carried bysaid shaft, means for operating the Worm gear from the operators seat,an elevating rudder connect- ,ed to partake of the adjusting movementimparted the stabilizing surface, and means for ogerating said rudderindependently of said a ustmg means.

14. In an aircraft, a longitudinally projecting frame, a horizontalstabilizing surface adustable about an axis extending transversely ofsaid frame, means for adjusting said surface from the operators seatincluding a self-locking mechanical device whereby the surface isretained in its adjusted position when the adjusting means is releasedby the operator, an elevating rudder, and operating means for saidelevating. rudder independent of said stabilizer adjusting means.

In testimony whereof I hereunto aflix my signature.

JOHN P. TARBOX.

